What does challenges ahead mean?

What tissue is microvilli and goblet cells associated with? If you view our solar system from ecliptic north what is the direction (clockwise or counterclockwise) of the orbit of Venus around the Sun Of the orbit of Earth around the Sun? When did plants start growing on Earth? What is sands friability? A metric ton is 1000 kilograms about hoe many pounds is this? What are characteristics of phospholipids? What controls activities like sneezing.coughing and swallowing? How many gallons of water are in a 3.5'X 15' swimming pool? What is the difference between a B vent and A vent? When do cells reproduce? Is it possible for your cuticle to come off? Why are aluminum alloys used instead of aluminum itself? What are the function of the female reproductive system? Why is Louis leakeys work important to society? When you cook pulses at mountain it will take more time or less than at sea level? What role did DNA play in the prosecution case? How much longer do most scientists believe the Sun will radiate? What does the name Grant mean as a name? Which outer planet has a mass that is twice that of all the other outer planets? How can you determine the mass of an unknown element from a mass of a known element?